1. Field of the Invention
The present invention is directed to an examining device and examining method, and more particularly, to an examining device and examining method used for examining a retardation value and a transmittance of a display panel.
2. Description of Related Art
Nowadays, multimedia technology has been well developed, which is benefited from the development of semiconductor devices and display apparatuses. As for displays, liquid crystal displays (LCDs) having advantages, such as high image display quality, good space utilization, low power consumption and radiation-free have gradually become the mainstream products of the market.
Taking a thin film transistor LCD (TFT-LCD) module for example, it is mainly consisted of an LCD panel and a backlight module. The LCD panel is consisted of a TFT array substrate, a color filter substrate (C/F substrate) and a liquid crystal layer disposed therebetween. The backlight module is used for providing the plane light source for the LCD panel so that the LCD module can achieve its desired display effects.
Usually, when a display panel is produced, the retardation value thereof is fixed. There is a certain relationship existing between the retardation value and the transmittance of the display panel, however, since a loss would occur when light emitting from the light source passes through the display panel, the transmittance obtained therefrom is lower than the actual transmittance of the display panel. For example, the transmittance of the display panel can be obtained through performing a laser light passing through the display panel and then dividing an original light intensity of the laser light by the light intensity of the laser light passing through the display panel. Ideally, when the transmittance is given, the retardation value can be inferred. However, the glass substrate, liquid crystal, polarizers, analyzers and pixel electrodes are possible to absorb or reflect the laser light so that the light intensity of the laser light is decayed. Thus, the retardation value obtained by the way of dividing the original light intensity of the laser light by the light intensity of the laser light passing through the display panel is not correct.
In other words, the retardation value obtained by such way can not correctly represent the actual retardation value of the display panel. Therefore, a measuring method of rotation polarizers is developed, for example, the one disclosed in Taiwan Patent No. TW00440737. However, such method requires a complicated system to control the rotation of the polarizers. The precision level of such measuring method is determined by how precisely the rotation of the palarizers is controlled.